Padstones, Bearings & Wall Plates Explained

When a beam, whether steel, concrete or timber, transfers its load into a masonry wall, the stress concentration at the bearing point can crush or crack the masonry beneath. A padstone solves this by spreading that point load over a larger surface area, keeping stress within safe limits for the blockwork or brickwork below.

Padstones are a small but frequently overlooked structural element. Omitting them, undersizing them, or using the wrong material is a common cause of cracking around lintels and beams, sometimes appearing months or years after a beam was installed.

Why Padstones Are Needed

The concrete blocks used in most houses are typically rated at 2.9–7.3 N/mm² (depending on block type), and even a high-strength aircrete block is rated at 7.3 N/mm².¹ A loaded steel beam in a house can deliver several tens of kilonewtons at each end bearing. Without a padstone, that load passes through only the end section of the steel onto the masonry, a contact area that can be as small as 100 mm × 100 mm. The resulting stress easily exceeds the blockwork’s capacity.

A padstone made from dense precast concrete (commonly manufactured to around 40–50 N/mm²) or Class B engineering brick (compressive strength at least 75 N/mm²) distributes that same load over a larger footprint, reducing the stress to within safe limits.²

The padstone also provides:

• A flat, level, mortar-bedded seating surface for the beam
• Protection against local spalling of the inner leaf when the beam deflects under load
• A defined bearing zone that can be inspected and recorded

Concrete vs Engineering Brick Padstones

Two materials dominate UK padstone practice:

For comparison, a 440 × 215 × 100 mm precast C40/50 padstone lists at £32.08 including VAT at Robert Price.³ Selco lists a 65 mm Class B engineering brick at £0.66 including VAT.⁴ Solid red Class B engineering bricks sold through B&Q cost £192 for a pack of 100, about £1.92 each.⁵ A solid blue Class A engineering brick lists at £2.36 including VAT at Lords Builders Merchants.⁶

In the UK, a Class A engineering brick has a compressive strength of at least 125 N/mm² and water absorption below 4.5%, and a Class B at least 75 N/mm² and below 7%.⁷ Engineering bricks are often used in pairs or multiples, bedded in a strong cement mortar, to achieve the required bearing area. Their high density and low water absorption also resist moisture wicking in damp-prone locations.

Precast concrete padstones are the most common choice for domestic beam insertions. They are supplied in standard sizes (see below) and can be ordered from builders’ merchants or structural suppliers. They are bedded in full-bed cement mortar before the beam is set on top.

Sizing Padstones

The padstone must be large enough to reduce the bearing stress to within the allowable capacity of the masonry beneath. Sizing is a structural engineering calculation, but the following rules of thumb give a starting point for standard domestic scenarios:

Minimum bearing length (the dimension along the beam span) is typically 100–150 mm for lintels and beams in domestic masonry. Approved Document A’s simple guidance for lintels assumes a bearing length of 150 mm, reduced to 100 mm where the clear span is 1.2 m or less.⁸ For heavier steel beams (UB 203 and above), 150–200 mm bearing is common.

Padstone footprint must be sized so that: load ÷ padstone area ≤ allowable bearing stress of the masonry below. Structural engineers use BS EN 1996-1-1 (Eurocode 6) and the UK National Annex for masonry design.⁹

Typical precast padstone sizes stocked by UK suppliers:

Stowell Concrete, for example, makes 440 × 215 × 140 mm and 440 × 215 × 100 mm padstones.²

For a standard loft conversion ridge beam or an RSJ replacing an internal wall in a 1930s terrace, a 440 × 215 × 140 mm or 440 × 215 × 215 mm precast padstone is typically specified. Your structural engineer should confirm this.

Spread Bearings and Alternative Solutions

Where an inner leaf is thin, or the masonry below is in poor condition, a padstone alone may not be sufficient. Options include:

Spreader plates: galvanised or grade S275 steel plates welded to or placed beneath the beam end. These spread load over a wider area than a padstone and are sometimes preferred in heavily loaded commercial scenarios.

Column bases: for point loads from posts or columns, a reinforced concrete column base or proprietary steel base plate is used rather than a padstone.

Joist hangers: where timber joists or beams meet a masonry wall, proprietary hangers to BS EN 845-1 (e.g. Simpson Strong-Tie or MiTek) can carry them instead of building the ends into the wall.⁸ A masonry hanger is built into a bed joint, so its load still passes into the wall by bearing and the masonry beneath it needs the same care as under a padstone.

Wall Plates

A wall plate is a horizontal timber member (typically 100 × 75 mm or 75 × 50 mm regularised treated softwood) bedded in mortar on top of an inner leaf or ring beam. It distributes concentrated rafter, truss or joist loads along the wall line, and provides a fixing surface for the structural members above.

Wall plates are standard practice in traditional roof construction:

• At eaves level: on top of the inner leaf of the cavity wall, supporting rafters or truss tails
• At floor level: where joists are to be fixed to a wall (in some masonry details)

Wall plates must be:¹⁰

• Preservative-treated where the risk calls for it, following BS 8417:2024 (timber preservation), which sets the treatment by use class
• Bedded level on a full bed of mortar
• Kept clear of the cavity and away from the outer leaf
• Continuous along the wall where possible, with scarf joints staggered

Wall Plate Straps

One of the most important and most frequently missed details in UK domestic construction is the holding-down strap connecting wall plates to the masonry below. Approved Document A, the guidance on Building Regulations Part A, calls for them to resist wind uplift: vertical strapping at least 1 m long at eaves level, at intervals of no more than 2 m.⁸ They can be left out only where the roof is pitched at 15° or more, is tiled or slated, is of a type known locally to resist wind gusts, and has its main timbers spanning onto the wall at no more than 1.2 m centres.⁸

Straps are galvanised steel (commonly 30 mm wide and at least 1 m long). They are fixed to the wall plate or rafters and down the inner face of the inner leaf at no more than 2 m centres.⁸

Omitting holding-down straps where they are needed is a serious structural deficiency. In high wind exposure zones (exposed coastal and upland areas), strap spacing may need to be reduced, refer to BS EN 1995-1-1 and the Timber Research and Development Association (TRADA) guides.

Used with Steel and Timber Beams

The padstone sits below the beam end, the beam sits on the padstone, and, in most domestic steel installations, a packing plate or thin grout bed levels the beam perfectly. For timber beams, the padstone is usually topped directly by the beam end without packing.

The sequence for a standard RSJ installation:

1. Build the masonry to the correct height, incorporating the padstone in the bed joint (or bedding the padstone on top of the masonry as a separate unit).
2. Prop the existing structure.
3. Cut the wall opening and set the padstone(s) level, with full mortar bedding.
4. Lower the steel onto the padstones (two operatives minimum; mechanical assistance for heavy sections).
5. Allow the mortar and any packing to gain enough strength before removing props, for the period your engineer specifies (often at least 48 hours, and longer in cold weather).

The padstone is always specified by the structural engineer who designs the beam. If a padstone size, specification or bearing length is not stated in the structural engineer’s drawings or calculations, ask before proceeding.